1. Field of the Invention
In general, the present invention relates to dentifrice compositions and more specifically to the extension of gum thickeners by replacement of a portion thereof with a silica thickener.
2. Description of the Prior Art
Present day toothpastes are composed of five essential components; that is, an abrasive material, a thickener material, a humectant system, flavor, and foaming agent. An excellent review entitled "Dentifrices" is presented by S. D. Gershon and Morton Pader in Cosmetics: Science and Technology, Volume 1, Second Edition, pages 423-531.
On page 490, the use of binders in dentifrices is discussed and the pertinent information is included here as a reference.
"Simple admixture of the solid and liquid phases of a toothpaste is inadequate to prevent separation of the liquid phase, particularly during storage. To avoid this, a binder is added. Essentially all binders are hydrophilic colloids which appear to dissolve but actually disperse, swell, or absorb water to form viscous liquid phases. By acting as protective colloids and by increasing the consistency of the mixture of liquid and solid phases of the toothpaste, the binder stabilizes the mass against separation of the liquid phase. PA0 Starch, which was generally employed in the form of glycerite of starch was one of the first binders employed. Gum arabic, ghatti, gums karaya and tragacanth, natural tree exudations, were prominent as binders during the early part of the twentieth century. Seaweed colloids, as represented by Irish moss and the alginates, have gained prominence. Water-dispersible derivatives of cellulose, prepared synthetically, have been utilized recently to an increasing extent. PA0 In addition to the organic binders, bentonite, a native colloidal, hydrated aluminum silicate, and Veegum, a complex colloidal magnesium aluminum silicate, have been recommended as binders."
In all dentifrice formulations, natural or synthetic, gum thickeners are used to provide the desired viscosity to the paste.
Viscarin is a thickener which is used in many dentifrices. It is refined water-soluble carrageenan extracted from certain red marine plants, reduced to a free-flowing powder by alcohol precipitation.
A synthetic thickener, CMC (carboxy methyl cellulose) is widely used in dentifrices.
The general procedure for using gum thickeners is that the thickener is first dispersed in the desired humectant system to form a gel. Then the other toothpaste ingredients are added to this gel.
Gum thickeners present many problems when these materials are used in locations of very high humidity; for example, in South America, Africa, and many Far East countries. Under the influence of high humidity conditions due to an enzyme attack, the gum thickener loses its efficiency. Both the CMC and viscarin lose their effectiveness to a considerable extent under high humidity conditions.
Normally, prior art dentifrice compositions which contain high loadings of water will contain about 1 wt. % of gum thickener. However, where the water content is low, the amount of thickener may similarly be lowered since there is less need for a large amount of thickener in the composition. Toothpaste compositions having low water contents and gum amounts of 0.2 to 2%, together with high contents of humectants, are shown in U.S. Pat. Nos. 3,934,000; 3,864,470; 3,935,306 and 3,689,637 for example. On the other hand, in dentifrice compositions which contain high water contents, e.g. in the range of 40 wt. %, about 1 wt. % of gum thickener is normally used as illustrated for example by U.S. Pat. No. 3,705,940.
The present invention provides a composition and method wherein dentifrice compositions having high water loadings can be formed with reduced amounts of gum thickeners.